1. Field
The field of the invention is endless track assemblies for snow grooming vehicles, and more particularly the cleat assemblies thereof, including structures for fastening the cleats to the flexible plastic belting of such tracks.
2. State of the Art
Snow groomer vehicles use endless tracks having flexible plastic belts made endless by connecting the ends with lacing or the like. The belts are often reinforced by plies of fabric incorporated into the rubber-like belt material. Steel cleats are bolted across the belts at intervals of a few inches. Each belt is engaged by a power-transmitting sprocket wheel, which forces the belt to travel around a set of guiding wheels called bogies. The powered belt imparts horizontal shear force to the cleats, which engage the snow to propel the vehicle. Much development has gone into the design of the elongate cleat members, with the object of providing maximum traction and resistance to side slipping. Typical cleat constructions are disclosed in U.S. Pat. Nos. 3,765,731, 4,560,211, 4,281,882 and 4,059,315. Typically, the ground contacting cleat, also called a grouser, is fastened to the outside of the flexible belting by bolts or rivets installed in matching holes in the cleat, belt, and a metal backing plate on the inside of the belt. The shanks of the bolts bear against a side of the holes in the belt to transfer the shearing force to the cleats, perhaps initially aided by friction between the belt and the cleat and backing plate. The belt material is malleable, and the fabric plies are discontinuous at the holes, so that the holes become permanently elongated by the concentrated stresses, loosening the cleats. The hole elongation occurs even with great clamping force between the cleat and the backing plate. This is because the belting material creeps under prolonged stress to relieve the clamping force and substantially eliminating the initially helpful friction between the belt and the cleats and backing plate. The use of increased numbers of holes and bolts, as indicated for example in U.S. Pat. No. 4,281,882, FIG. 8., helps somewhat. However, the belting is correspondingly weakened, so that this solution is self-limiting and has not prove satisfactory.